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Representing USE-OR in SKOS/XL/ISO25964

From: Osma Suominen <osma.suominen@helsinki.fi>
Date: Tue, 22 Apr 2014 17:55:26 +0300
Message-ID: <535682DE.5030302@helsinki.fi>
To: public-esw-thes@w3.org
Hi all!

I have seen many thesauri include a USE-OR relationship, that is, a 
pointer from an ambiguous term (homograph) to several alternative 
meanings (terms or concepts). For example (taken from ISO25961-1, 
section 8.5),

pitch
USE audio frequency
OR  gradient

ISO25964-1 recommends against this practice, and instead suggests adding 
qualifiers to avoid having ambiguous terms in the thesaurus. So you 
would only have "pitch (sound)" and "pitch (steepness)" as preferred terms.

However, some thesauri I'm familiar with (e.g. NAL Thesaurus, CAB 
Thesaurus, YSO) like to include pointers to this kind of either-or 
combinations, for various reasons, including the need to support legacy 
metadata which use the ambiguous term, or to store provenance 
information. How could this be represented using SKOS / SKOS-XL / 
iso-thes / RDF in general? I can think of three ways:


1. Plain SKOS, just use altLabels

ex:A a skos:Concept;
   skos:prefLabel "pitch (sound)"@en ;
   skos:altLabel "pitch"@en .

ex:B a skos:Concept;
   skos:prefLabel "pitch (steepness)"@en ;
   skos:altLabel "pitch"@en .

This is simple, but the ambigous term "pitch" only appears as a literal, 
so it doesn't get a URI (which could be useful, e.g. when converting 
legacy textual metadata that uses the ambiguous term), and you can't 
easily include provenance information about "pitch", such as the date 
when the split was made.


2. SKOS XL, one shared label instance

ex:A a skos:Concept ;
   skosxl:prefLabel ex:pitch_sound ;
   skosxl:altLabel ex:pitch .

ex:A a skos:Concept ;
   skosxl:prefLabel ex:pitch_steepness ;
   skosxl:altLabel ex:pitch .

ex:pitch_sound a skosxl:Label ;
   skosxl:literalForm "pitch (sound)"@en .

ex:pitch_steepness a skosxl:Label ;
   skosxl:literalForm "pitch (steepness)"@en .

ex:pitch a skosxl:Label ;
   skosxl:literalForm "pitch"@en .

This way the ambiguous label gets at least a URI, though it's not a 
skos:Concept, which may or may not be a good thing depending on the 
requirements.


3. iso-thes SplitNonPreferredTerm with custom USE-OR property

ISO 25964 has a class SplitNonPreferredTerm which can be used to 
represent "an 'imagined' concept that may exist in a userís mind but is 
not present in the thesaurus". Though this class is normally used with 
the USE+ relation, one could coin a custom USE-OR property (below called 
ex:orUseTerm) and use it instead, like this:

ex:A a skos:Concept ;
   skosxl:prefLabel ex:pitch_sound ;
   skosxl:altLabel ex:pitch .

ex:A a skos:Concept ;
   skosxl:prefLabel ex:pitch_steepness ;
   skosxl:altLabel ex:pitch .

ex:pitch_sound a skosxl:Label ;
   skosxl:literalForm "pitch (sound)"@en .

ex:pitch_steepness a skosxl:Label ;
   skosxl:literalForm "pitch (steepness)"@en .

ex:pitch a isothes:SplitNonPreferredTerm ;
   skosxl:literalForm "pitch"@en ;
   ex:orUseTerm ex:pitch_sound, ex:pitch_steepness .

This is very similar to solution 2, but adds explicit links from the 
ambiguous label to the recommended labels. One could also link directly 
to the concepts, which in my view would make sense, but this is now 
modelled in the same way as USE+ in iso-thes, so the relationship is 
between labels only.


What would you do?

-Osma

-- 
Osma Suominen
D.Sc. (Tech), Information Systems Specialist
National Library of Finland
P.O. Box 26 (Teollisuuskatu 23)
00014 HELSINGIN YLIOPISTO
Tel. +358 50 3199529
osma.suominen@helsinki.fi
http://www.nationallibrary.fi
Received on Tuesday, 22 April 2014 14:55:55 UTC

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